Cardiopulmonary bypass is often used during cardiovascular surgeries, including coronary artery bypass grafting, valvular repair or replacement, septal defect repair, and pulmonary stenosis surgeries. To establish cardiopulmonary bypass, an arterial cannula is typically introduced into the aorta to deliver oxygenated blood from a bypass-oxygenator machine.
It is known that embolic material, including tissue debris, calcium, atheromatous plaque, and/or thrombi are often generated during cardiovascular procedures, especially during clamping and unclamping of the aorta. Such embolic material often travels downstream to small vessels of vital organs, causing tissue ischemia or infarction. For example, transient ischemic attack (TIA) and cerebral infarction (stroke) are common complications of coronary artery bypass grafting surgeries.
To reduce the risk of distal embolism, arterial cannulas which include a blood filter device have been developed, allowing the filter to capture loose embolic material once the cannula is introduced into the vessel. Generally such devices include an expandable frame, such as an inflation seal or an umbrella frame, and a filter mesh attached to the frame, the mesh being adapted to capture embolic material of a predetermined minimum size. The frame may be attached externally to the distal end, or alternatively, it may be retractably deployed from a lumen within the cannula.
However, there are several disadvantages associated with the use of a cannula with such a filter device. First, the expansion frame is often rigid. When the filter is expanded in a vessel, any movement of the cannula will cause displacement of the filter within the vessel, and cause the frame to scrape against the vascular wall, resulting in vascular damage, e.g., dislodgement of plaque, hemorrhage, or dissection. Second, the proximal end of the filter device is often rigid and contributes to crowding of the surgical field, especially in minimally invasive procedures.
Thus, there is a need for a filter device for use with an arterial cannula that minimizes the rigidity of the filter device and the expansion frame of the filter, thereby reducing the risk of vascular wall injury.